Guitar construction



Oct. 28, 1969 c. H. KAMAN GUITARv CONSTRUCTION Filed Jan. 27. 19 67 3 Sheets-Sheet 1 INVENTOR. mam A. MMAA/ Oct. 28, 1969 c. H. KAMAN GUITAR CONSTRUCTION 3 Sheets-Sheet 2 Filed Jan. 27. 1967 Oct. 28, 1969 c. H; KAMAN GUITAR CONSTRUCTION 3 Sheets-Sheet 5 Filed Jan. 27. 1967 United States Patent 3,474,697 GUITAR CONSTRUCTION Charles H. Kaman, Simsbury, Conn., assignor to Kaman Corporation, Bloomfield, Conn., a corporation of Connecticut Filed Jan. 27, 1967, Ser. No. 612,180

Int. Cl. Gd N08 US. Cl. 84-267 6 Claims ABSTRACT OF THE DISCLOSURE Background of the invention This invention relates in general to string musical instruments and deals more particularly with a guitar construction.

In a guitar a musical tone produced by a string is intensified and enriched by supplementary vibration induced in the resonating cavity of the soundbox and in the soundboard of the instrument. Accordingly, it is generally desirable that the soundbox and particularly the soundboard which forms a part thereof be of relatively light construction for effective sound production. However, the general cantilever arrangement of the neck of the instrument relative to the soundbox and the forces exerted by the strings upon the soundbox, the neck and the connection therebetween impose structural requirements which must be met. In the construction of a guitar some compromise is therefore necessary and structural strength and durability is often attained in an instrument at sOme sacrifice of the sound production qualities thereof. The general aim of this invention is therefore to provide a guitar wherein qualities of structural strength and durability are attained with minimal compromise of sound production quality.

Summary of invention In accordance with this invention a guitar is provided which has a soundbox of relatively light construction including an impregnated fabric body and a thin wooden soundboard. The soundboard is flexibly reinforced and v is preferably tapered and arranged relative to the body to provide structural strength in critical regions and to permit maximum excursion thereof for great resonance and timbre. The soundbox is further structurally reinforced around the point of connection with the neck to resist neck deflection relative thereto and deformation of the soundbox caused by tension of the instrument strings. Provision is also made to compensate for bowing of the neck caused by string tension.

.Brief description of drawings FIG. 1 is a plan view of a guitar constructed in accordance with the present invention, a portion of the soundboard being broken away to reveal the supporting structure therebelow.

" FIG..2. is a side elevational view of the guitar of FIG. 1, a portion of the body side wall being broken away to further reveal the instrument structure.

FIG. 3 is a transverse sectional view through the guitar of 'FIG. 1 taken along the line 3-3 of FIG. 1.

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FIG. 4 is a transverse sectional view generally similar to FIG. 3 but taken along the line 44 of FIG. 1.

FIG. 5 is a transverse sectional view generally similar to FIG. 3 but taken along the line 5--5 of FIG. 1.

FIG. 6 is a longitudinal sectional view taken along the line -6-6 of FIG. 2 and shows the soundbox with the neck removed therefrom.

FIG. 7 is a somewhat enlarged fragmentary longitudinal section along the line 77 of FIG. 1.

FIG. 8 is a somewhat enlarged transverse sectional view taken along the line 8-8 of FIG. 1.

FIG. 9 is a somewhat enlarged transverse sectional view taken along the line 9-9 of FIG. 1.

FIG. 10 is a fragmentary longitudinal sectional view taken along the line 1010 of FIG. 7.

Detailed description of preferred embodiment Referring now to the drawings and first particularly to FIGS. 1 and 2, a guitar embodying the present invention and indicated generally at 10 is shown to comprise a. hollow soundbox 12 including a bowl-shaped body 14 and a relatively thin soundboard 16 having a sound opening 18. Extending upwardly from the soundbox 12 is an elongated neck 20 terminating in a peghead 22, provided with pegs for six strings 24, 24, and carrying a fret board 26. The strings 24, 24 extend between the peghead and a bridge 28 secured to the soundboard 16.

The bowl-shaped body 14, as it is shown in FIG. 2, includes a gently inwardly curving waist characteristic of a conventional guitar. An impregnated fabric is preferably used to make the body which is relatively thin walled. The body is of a substantially uniform thickness, terminates in a forward edge 32, and has an acoustically reflective inner surface 34 at least a portion of which is generally parabolic. The body includes a two-dimensionally curved or arched rear portion 36, best shown in FIGS. 3-5, and has an integral side portion 38 including generally U-shaped upper and lower bouts, respectively indicated at 40 and 42, connected by inwardly curved central bouts 44, 44 which form the waist of the instrument. The side portion 38 adjacent its forward edge 32 is substantially perpendicular to the soundboard 16. In planes perpendicular to the soundboard it extends in an approximate straight line rearwardly from the soundboard for a substantial distance and then curves inwardly to smoothly blend with the arched rear portion 36. The side portion 38 therefore spaces the back portion 36 from the soundboard and the back portion hasa relatively broad or gentle curvature, and thereby a generally conventional front to rear thickness of the soundbox'is maintained while allowing the rear wall to provide a broadly curved acoustically reflective surface. A forwardly opening and rearwardly extending slot 46 is formed in the side portion 38 centrally of the'upper bout 40 for receiving a portion of the neck, as best shown in FIG. 10. Preferably, the body is made from plies of glass fabric preimpregnated with epoxy resin and laminated to a thickness of approximately 0.036 inch. This body construction has been found to give the instrument particularly desirable sound production qualities when used in combination with a soundboard constructed as hereinafter described.

Reinforcement for the body around the point of its connection to the neck is provided by a generally circular reinforcing pad 48 preferably made of the same material of which the body is made and bondedto the inner surface 34 of the body adjacent the slot 46. The neck 20 is connected to the soundbox 12 by a neck support block 50 bonded to the body inner surface 34 and bearing against both the upper bout 40 and the pad 48. A forwardly and upwardly opening recess or dove-tailed groove 52 formed in the block 50 receives an associated portion of the neck 20 as hereinafter further described.

The front of the soundbox 12 is formed by the soundboard 16 having substantially planar front and rear surfaces respectively indicated at 54 and 56. Structural connection between the soundbox 16 and the body 14 is provided by an elongated generally L-shaped angle member 58 generally conforming to the shape of the inner body surface 34 adjacent its forward edge 32. The angle member 58 includes 'a leg 60 bonded to the inner surface 34 and a leg 62 having a forwardly facing surface disposed vgenerally within a plane defined by the body forward edge 32. The leg 62 is in turn bonded to the soundboard rear surface 56.

The soundboard 16 is longitudinally tapered from a maximum thickness at its upper end to a minimum thickness at its lower end, as best shown in FIG. 2. For structural reasons it is desirable that the soundbox be of greatest strength in the region where the neck is joined thereto, and for this reason the soundboard is of greatest thickness in this upper region. The tapered configuration of the soundboard provides ample thickness in the region of the sound opening 18 and the bridge 28 while the decrease in thickness in the region of the lower bout 42 permits maximum excursion in the latter region. For added strength and durability it is desirable that the soundboard be further reinforced. Accordingly, a plurality of relatively flexible wooden ribs are *adhesively bonded to the soundboard rear surface 56 and are arranged in a manner illustrated in FIG. 6. A relatively heavy rib 64 extends transversely of the soundboard between the sound opening 18 and the upper bout 40 to reinforce the longitudinally extending grain structure of the board in the region of the neck connection. Diagonally extending ribs 66 and 68, somewhat lighter than the rib 64, cross each other below the sound opening 18 and in the vicinity of the bridge 28. Further reinforcement is provided in the bridge region by a thin gusset plate 70 secured to the rear surfaces of the ribs 66 and 68 proximate the point of crossing. Relatively light reinforcing ribs 72, 74 and 76 cooperate with the aforedescribed ribs 64, 66 and 68 to form a reinforcing structure surrounding the sound opening 18. In the lower region of minimum thickness the soundboard 16 is further flexibly reinforced by at least one elongated fabric strip 77 bonded to the rear surface 56 and extending transversely thereof.

The soundboard 16 is assembled with the body 14 to form the soundbox 12 before the neck 20 is connected thereto. For this reason the soundboard is provided with an upwardly opening notch 78 at its upper end which is generally aligned with the forward end of the groove 52 in the neck support block 50, as best shown in FIG. 6. The notch 78 permits a portion of the neck to be inserted in the groove 52.

Considering now the neck 20 in further detail, and referring particularly to FIGS. 7-10, it is preferably made from laminated wood, which gives it great strength and generally enhances the appearance of the instrument. At its lower end the neck has an extending portion or flared tongue 80 which passes through the body slot 46 and interlockingly engages the block 50 by being received in the groove 52. Formed in the neck is a cavity or bore 82 extending longitudinally therethrough and communicating at its upper end with a somewhat larger recess 84. The latter recess opens through the forward surface of the peg head 22 and has a bearing surface 86 at the lower end thereof. A removable cover plate 88, see FIG. 1, fastened to the forward surface of the peg head 22 conceals the recess 84. Preferably, the centerline of the bore 82 lies on an arc of a circle having its center spaced forwardly of the neck and on a line 90 normal thereto and passing generally centrally therethrough. Thus, a central portion of the bore wall, indicated at 92, is spaced rearwardly of the end portion thereof. The neck 20 further includes a forwardly facing surface 94 which lies generally within the plane 'of' the soundboard front surface 54 and which forms a generally straight line continuation thereof as viewed in FIG. 7. The fret board 26 is bonded to the neck surface 94 and overlies the portion of the soundboard in which the notch 78 is located, thereby concealing it from view.

Tension force exterted by the strings 24, 24 tends to urge the free end portion of the neck 20 forwardly relative to a straight line continuation of the soundboard. That is, it tends to bow the neck so as to increase the spacing between the strings and the fret board. To com"- pensate for string tension and overcome bowing of the neck, a generally longitudinally extending tension member or rod 96 is received Within the bore 82 and is provided with end portions which bear against associated opposite end portions of the neck. At its lower end the rod 96 carries a bearing plate 98 recessed in the tongue and bearing against a lower surface of the neck 20. A nut 100 is threadably received on the upper end of the rod 96 within the recess 84 and engages the bearing surface 86 to provide a means for adjusting the tensioning force exerted by the rod upon the neck 20. Access to the adjusting nut 100 is gained by removing the cover plate 88.

The bore wall central portion 92 urges the associated central portion of the rod 96 rearwardly or out of longitudinal alignment with the end portions thereof. As tension force exerted by the rod 96 upon the neck 20 is increased the rod tends to straighten or seek a longitudinally aligned position thereby exerting a generally forwardly directed force upon the bore wall central portion 92 to urge the free end portion of the neck rearwardly. Thus, by adjusting the nut 100 proper spacing between the strings 24, 24 and the fret board 26 may be maintained.

In a playing position the body of the instrument may be rested or steadied against a part of the players body, as for example his foreleg. For this reason it is desirable that at least a portion of the outer surface of the instrument body be of a non-skid character. In the illustrated guitar 10 the outer surface of the body 14 has a nonskid portion 102 in the vicinity of one central bout 44 and best shown in FIG. 2. The non-skid surface portion has a coefficient of friction substantially greater than the coefficient of friction of the remainder of the body outer surface.

The drawing shows a preferred embodiment of the invention and such embodiment has been described, but it will be understood that various changes may be made from the construction disclosed and that the drawings and description are not to be construed as defining or limiting the scope of the invention.

The invention claimed is:

1. In a guitar, the combination comprising a hollow soundbox including a substantially rigid bowl-shaped body made from impregnated fabric and having a relatively thin wall of substantially uniform thickness, said wall having an acoustically reflective inner surface and including a vaulted back portion and a side portion terminating in a forward edge and including an upper bout and a lower bout and inwardly curved central bouts providing connection therebetween, a wooden soundboard which tapers from a maximum thickness at its upper end to a minimum thickness at its lower end secured to said body at said forward edge, said soundboard forming a front for said soundbox and having substantially planar front and rear surfaces and a sound opening therethrough, an elongated neck extending upwardly from said upper bout, and means connecting said neck to said soundbox.

2. In a guitar, the combination comprising a hollow soundbox including a substantially rigid bowl-shaped body made from impregnated fabric and having a relatively thin wall of substantially uniform thickness, said wall having an acoustically reflective inner surface and including a two-dimensionally curved back portion and a side portion terminating in a forward edge and including an upper bout and a lower bout and inwardly curved central bouts providing connection therebetween, a wooden soundboard secured to said body at said forward edge forming a front for said soundbox and having substantially planar front and rear surfaces and a sound opening therethrough, an elongated neck extending upwardly from said upper bout, means connecting said neck to said soundbox, and a reinforcing pad bonded to said back portion inner surface generally adjacent said upper bout and proximate the point of connection between said neck and said soundbox body.

3. In a guitar, the combination as set forth in claim 2. and wherein said means for connecting said neck to said soundbox comprises a block bearing against said pad and bonded to said side portion inner surface, said block having a generally forwardly and upwardly opening groove therein aligned with an opening through said body wall side portion, said neck having an end portion extending through said wall opening and interlockingly engaging said block within said groove.

4. In a guitar, the combination as set forth in claim 3 further characterized by said soundboard having a notch therethrough generally laterally aligned with said block groove to permit said neck end portion to be inserted into said groove after said soundboard and said body are assembled, and a fretboard overlying a portion of said neck and that portion of said soundboard including said notch.

5. In a guitar. the combim'ttiou ccnuprisiug a hollow soundbox including a substantially rigid howl-shapcd body made from resin impregnated fabric and having a relatively thin wall of substantially uniform thickness,

said wall having an acoustically reflective inner surface and including a back portion and a side portion terminating in a forward edge, a wooden soundboard secured to said body at said forward edge forming a front for said soundbox and having substantially planar front and rear surfaces and a sound opening therethrough, said soundboard being tapered from a maximum thickness at its upper end to a minimum thickness at its lower end, an elongated neck extending upwardly from the upper end of the said body, and means connecting said neck to said soundbox.

6. In a guitar, the combination as set forth in claim 5 further characterized by at least one elongated fabric reinforcing strip extending generally transversely of said soundboard and adhesively bonded to the rear surface thereof.

References Cited UNITED STATES PATENTS 1,446,758 2/1923 McHugh 84293 3,159,072 12/1964 Burns et al. 84293 FOREIGN PATENTS 255,211 7/ 1926 Great Britain.

OTHER REFERENCES National, Valco Guitars Inc.; Distributor: Fred Gretsch Mfg. Co., Chicago, lII., Dec. 7, 1964, page C.

, RKHARI) I). WILKINSON, Primary Examiner .I I. GUN/AIRS. Assistant Ixzuuiuer us. or. x12. S t- 291 

